Multimedia communication using co-located care of address for bearer traffic

ABSTRACT

In a wireless communications system in which a mobile node seeks a communication session with a correspondent node by first signaling for initialization of the communication session through a first data path via an intermediate node. Thereafter, contents of the communication is established through a second data path in which the mobile node and the correspondent node communicate straightforwardly without going through the intermediate node.

CLAIM OF PRIORITY UNDER 35 U.S.C §119

The present Application for Patent claims priority to U.S. ProvisionalApplication No. 60/561,955, entitled “Service Based Policy for Mobile IPCo-location Care of Address,” filed Apr. 13, 2004, and assigned to theassignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

I. Field

The present invention generally relates to packet data communications,and more particularly, to wireless multimedia packet data communicationsusing separate communication paths for signaling and for contenttransmitting.

II. Background

Interconnecting of networks globally allows information to be swiftlyaccessed irrespective of geographical distances. FIG. 1 shows asimplified schematic drawing of the global connection of networks,commonly referred to as the Internet signified by the reference numeral20. The Internet 20 is in essence many networks with different levels ofhierarchy linked together. The Internet 20 is operated under the IP(Internet Protocol) promulgated by the IETF (Internet Engineering TaskForce). Details of the IP can be found in RFC (Request For Comments) 791published by the IETF.

Connected to the Internet 20 are various individual networks, sometimescalled LANs (Local Area Networks) or WANs (Wide Area Networks) dependingon the network sizes. Shown in FIG. 1 are some of such networks 22, 24,26 and 28 tied to the Internet 20.

Within each of the networks 22, 24, 26 and 28, there can be variouspieces of equipment connected to and in communication with each other.Examples are computers, printers, and servers, to name just a few. Eachpiece of equipment has a unique hardware address, commonly called theMAC (Media Access Control) address. The piece of equipment with the MACaddress is sometimes called a node. When the node communicates beyondits own network via the Internet 20, an IP address needs to be assignedto the node.

The assignment of the IP address can be manual or automatic. The manualassignment of the IP address can be performed by a networkadministrator, for example. More often, the IP address is automaticallyassigned. For instance, in a LAN, the IP address can be assigned by aserver called the DHCP (Dynamic Host Control Protocol) server residinginside in the node's LAN. In a WAN which supports wireless technologies,IP address can even be assigned automatically and remotely.

Returning now to FIG. 1, as an example, suppose a node 30 in the network22 attempts to send a data packet to another node 32 in the network 28.Under the IP, each data packet needs to have a source address and adestination address. In this case, the source address is the address ofthe node 30 in the network 22, and the address is called the HoA (HomeAddress). The destination address is the address of the node 32 in thenetwork 28.

As another example, when the node 30 in the network 22 tries to retrieveinformation from the node 34 in another network 24, such as in a webhosting session in which the node 34 serves as a web server, the node 30must provide a proper IP address of the node 34 in the network 24 forsuch a session.

Advent in wireless technologies allows nodes to move away from theiroriginally registered network to another network. For instance,referring back to FIG. 1, the node 30, instead of permanently wired tothe network 22, can be a wireless device, such as a PDA (Personal DeviceAssistant), a cellular phone, or a mobile computer. The wireless node 30can travel beyond the boundary of its home network 22. Thus, forinstance, the node 30 may roam away from its home network 22 to aforeign network 26. Under such scenario, the original HoA assigned tothe node 30 would no longer be applicable to the node 30. As such, datapackets destined to the HoA of the node 30 may not be reachable to thenode 30.

The MIP (Mobile Internet Protocol) set forth by the IETF is intended toaddress the node mobility problems. In accordance with the RFC 2002published by the IETF, whenever away from the home network 22 androaming in another network, the node 30 is assigned a “care-of address,”abbreviated as CoA (Care-of Address). Under the RFC 2002, there are twotypes of CoA, namely, the FA CoA (Foreign Agent Care-of Address) and theCCoA (Co-located Care of Address).

The FA CoA is in essence the address of a FA (Foreign Agent) which is adesignated server in the foreign network where the node 30 is locatedat.

The CCoA is an individual but temporary address assigned to the node 30by the foreign network.

In any case, anytime the node 30 is in a foreign territory, the node 30must register the CoA, be it the FA CoA or the CCoA, with its homenetwork 22, so that the home network 22 always knows the whereabouts ofthe node 30. After registration, the CoA is stored in the routing tablemaintained by a designated server, called the HA (Home Agent) 25 of thehome network 22.

Take a couple of examples for illustration.

For the case of the FA CoA, suppose the node 30 roams into the foreignnetwork 26. Upon reaching the territorial limit of the foreign network26, the node receives an advertisement message from the foreign network26 informing the node 30 of its presence in the foreign territory. Fromthe advertisement message, the node knows the address of the FA 36 ofthe foreign network 26. The node 30 then registers the FA CoA with theHA 25 in the home network 22.

When the node 30 in the foreign network 26 sends out a data packet tothe node 34 in the network 24, for example, knowing the address of thenode 34 in the network 24, the data packet can be sentstraightforwardly. That is, in accordance with the IP, in the datapacket, the source address can be set to the HoA of the node 30 and thedestination address can be set to the address of the node 34 in thenetwork 24. The direction of the data packet is shown as data path 38shown in FIG. 1.

As for the reverse data traffic, it is not as straightforward. In thereverse data route, when the node 34 in the network 24 attempts to senda data packet to the node 30, now in the foreign network 26, asmentioned above, in conformance with the IP, both the source and thedestination addresses must be specified in the data packet. In thiscase, the source address is the IP address of the node 34 in the network24. As for the destination address, the node 34 only knows the HoA ofthe node 30, not the FA CoA of the node 30. Thus, the destinationaddress will be set to the HoA of the node 30. Nevertheless, since theFA CoA of the node 30 is stored in the routing table of the HA 25 in thehome network 22, when the data packet reaches the home network 22, theHA 25 of the network 22 encapsulates the received data packet with thestored FA CoA and sends it to the node 30 in the foreign network 26.That is, the encapsulated data packet utilizes the FA CoA as thedestination address. Once the foreign network 26 receives theencapsulated data packet, the FA 36 merely strips away the encapsulatedFA CoA and delivers the original packet to the mobile node 30. The routeof the data packet is shown as data path 40 in FIG. 1.

It also be noted that the data paths, such as paths 38 and 40, inreality pass through the Internet 20 many times. For the sake of clarityso as not to obscure FIG. 1, the paths merely are shown as passingthrough the relevant servers, such as the HA 25 and the FA 36. That is,the data paths 38 and 40 are shown as logical paths as shown in FIG. 1.

Operating in the manner as described above, the mobile node is said tobe communicating with the correspondent node 34 under the MIP using FACoA.

As for the case of the CCoA, when the node 30 roams away from the homenetwork 22, instead of requesting for a FA CoA, the node 30 can insteadrequest a CCoA via a DHCP server in any foreign network where the node30 is located at, for example. It should be noted that, if the network26 is a WAN supporting wireless technologies such as the cdma2000standards promulgated by the TIA/EIA (Telecommunications IndustryAssociation/Electronic Industries Association), the CCoA can berequested and assigned remotely by the foreign network 26 via a PPP(Point to Point Protocol) as set forth in the MIP. However, other thanthe assignment of the CCoA by the foreign network 26, the node 30performs all the functions of a foreign agent, such as the FA 36. Again,the MN 48 needs to register the CCoA with the HN 44.

For instance, to correspond with node 34 in the network 24, the node 30sends out a data packet with two layers of addresses. In the outerlayer, the source address is set as the CCoA, and the destinationaddress is set as the HA 25. In the inner layer, the source address isthe HoA of the node 30 and the destination address is the address of thenode 34 in the foreign network 24. Upon receipt of the data packet fromthe roaming node 30, the HA 25 strips off the outer address layer andsends the data packet to the node 34 with the inner address layer. Thelogical path of the data packet is shown as data path 42 in FIG. 1.

In the reverse data path, that is, when the node 34 sends a data packetto the node 30, the data packet has only one address layer with thesource address set to the node 34 and the destination address set to theHoA of the node 30. Upon receipt of the data packet, the HA 25encapsulates the data packet with the CCoA as the destination addressand the address of the HA 25 as the source address and sends theencapsulated data packet to the node 30. The node 30 performs thede-encapsulating on its own without going through the FA 36. Thedirection of the data packet is shown as data path 44 in FIG. 1.

Operating in the manner as described above, the roaming node 30 is saidto be communicating with the correspondent node 34 under the MIP usingthe CCoA.

Irrespective of whether the node 30 uses the FA CoA or the CCoA, tocommunicate with other networks under the MIP while the node 39 isroaming, there are considerable traffic detours of data paths asexemplified by the logical data paths 40, 42, and 44 shown in FIG. 1.That is, data packets have to pass through intermediate networks beforereaching the destination. Such traffic detours do not pose much of aproblem in certain types of data, such as data in a file transfer. Underthe TCP (Transmission Control Protocol) as set forth in the RFC 793, thedata packets merely take a longer time to reach the destination. It isalso well known that data packets passing through longer data paths aremore susceptible to transmission errors. Nevertheless, the defectivepackets can always be resent, albeit further slowing down the overalldata transmission process. However, for other types of data, such as inan audio or video call, accurate access of real-time information is ofsignificant importance. Excessive detours of data routes introduceadditional latency during the data delivery processes. Furthermore, fordata packet sent under the UDP (User Datagram Protocol) as set forth inthe RFC 768, erroneous packets are not normally re-transmitted butsimply dropped. As a consequence, quality of service can be undermined.

Accordingly, there is need to provide better real-time data access in awireless communication system.

SUMMARY

In a communication system in which a mobile node seeks a communicationsession with a correspondent node by first signaling for initializationof the communication session through a first data path via anintermediate node. Thereafter, contents of the communication session isestablished through a second data path in which the mobile node and thecorrespondent node communicate straightforwardly without going throughthe intermediate node.

In accordance with one embodiment, the mobile node roams from its homenetwork to a foreign network. Using a first address, the mobile nodesignals for initiation of the communication session with thecorrespondent node via a home agent in the home network. The home agentin turn relays the initiation signaling to the correspondent nodelocating at a remote network. Upon acceptance by the correspondent node,the mobile node uses a second address to transmit contents of thecommunication session straightforwardly through a direct data pathbetween the mobile node and the correspondent node, without passingthrough the home agent. Consequently, with the shorter data path,transmission latency and transmission errors are curtailed, resulting inhigher quality of service. These and other features and advantages willbe apparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in whichlike reference numerals refer to like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the global connection of networks;

FIG. 2 is a schematic drawing showing an embodiment of the invention;

FIG. 3 is a flowchart showing the steps for initiation signaling andestablishing content traffic in accordance with the embodiment of theinvention;

FIG. 4 is a flowchart showing the steps of continuating with the contentflow by the process of update signaling in accordance with theembodiment of the invention; and

FIG. 5 is a schematic drawing of the circuitry of a mobile nodeconfigured in accordance with the invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the invention. Details are set forth in thefollowing description for purpose of explanation. It should beappreciated that one of ordinary skill in the art would realize that theinvention may be practiced without the use of these specific details. Inother instances, well-known structures and processes are not elaboratedin order not to obscure the description of the invention withunnecessary details. Thus, the present invention is not intended to belimited by the embodiments shown, but is to be accorded with the widestscope consistent with the principles and features disclosed herein.

The embodiments described below are operable according to the IMS/MMD(IP Multimedia Subsystem/Multimedia Domain) standards promulgated by the3^(rd) Generation Partnership Project (3GPP) and the 3^(rd) GenerationPartnership Project 2 (3GPP2). A general discussion of the IMS/MMD canbe found in published documents, entitled “3^(rd) Generation PartnershipProject: Technical Specification Group Services and System Aspects, IPMultimedia Subsystem (IMS), Stage 2,” 3GPP TS 23.228 “3^(rd) GenerationPartnership Project: Technical Specification Group Core Network,End-to-end Quality of Service (QoS) Signaling Flows,” 3GPP TS 29.208;and “IP Multimedia System, Stage 2,” TIA-873-002 and 3GPP2 X.P0013-012.

IMS is applicable in a wide variety of standards such as the cdma2000 bythe TIA/EIA, WCDMA by the 3GPP, and various other WANs.

Reference is now directed to FIG. 2 which schematically shows anexemplary embodiment of the invention. The overall system is generallysignified by the reference numeral 50 which includes a backbone network52, such as an intranet or the Internet.

By way of example, as shown in FIG. 2, connected to the backbone network52, among other networks, are a HN (Home Network) 54, a FN (ForeignNetwork) 56, another FN 57, and a RN (Remote Network) 58.

In the HN 54, there is a HA (Home Agent) 62 which assumes the duty ofmanaging data traffic within the HN 54 and also for controlling the datatraffic of the HN 54 for inbound and outbound routing. Furthermore,there is a PDSN (Packet Data Serving Node) 64 which in essence is anaccess gateway between the backbone network 52 and the radio accessportion of the HN 54.

To execute the various IMS/MMD functions and features, service providersinstalled different servers in the HN 54. Examples of such serversinclude a P-CSCF (Proxy Call State Session Function) server 70, and aS-CSCF (Serving Call State Session Function) server 72. The functionaldescription of these servers will be depicted later along with theoperational illustration of the system 50.

In addition to the nodes described above, there are other nodes withinthe HN 54 but are not shown for purpose of clarity. Such nodes can becomputers of various scales, printers, and any other devices which canbe mobile or non-mobile.

Shown in FIG. 2 are FNs 56 and 57 linked to the backbone network 52.Furthermore, for simplicity and ease of explanation, the FN 56 and theRN 58 are illustrated as somewhat similar to the HN 54. It should beappreciated that, depending on usage, the FN 56 and RN 58 can bestructured very differently. Thus, in this case, the FN 56 alsoincludes, among other things, a FA (Foreign Agent) 66, a PDSN 68, aP-CSCF 71, and a PDF (Policy Decision Function) 75. Likewise, the RN 58also includes, among other things, a PDSN 78, a P-CSCF 80, a S-CSCF 82,and a PDF 84.

In the system 50, there is a MN (Mobile Node) 60 which is originallyregistered with the HA 62 in the HN 54 with a HoA (Home Address). The MN60 is capable of migrating to other foreign networks, such as the FN 56or the FN 57, and can gain access to the backbone network 52 via the FN56 or the FN 57 under the MIP (Mobile Internet Protocol).

Suppose the MN 60 is roaming in the FN 56. In this specific example,assume the user of the MN 60 wants to have a video conferencing sessionwith a another user operating a CN (Correspondent Node) 90 in the RN 58.The node 90 can be mobile or non-mobile.

Conventionally, upon reaching the territory of the FN 56, the MN 60acquires the address of the FA 66 via advertisement by the FN 56. The MN60 then registers the FA CoA with the HA 62 in the HN 54 so that the HA62 can keep track of the locality of the MN 60.

Thereafter, the MN 60 in the FN 56 sends a message to the P-CSCF 70 inthe HN 54 to initiate the conferencing session. The initial signalingpath for the request starts from the FN 56 to the HN 54 before reachingthe RN 58. Likewise, if the conferencing session request is approved,the response signaling path is the reverse of the request path, that is,from the RN 58, to the HN 54 and then the FN 56. Upon approval of therequest, the bearer traffic, that is, the traffic of the media flowwhich contains the audio and video contents of the conferencing sessionpropagates more or less along the directions of the signaling paths.That is, the logical path of the bearer traffic flows from MN 60 in theFN 56, and then to the HA 62 in the HN 54 and finally to the RN 58before reaching the CN 90, and vice versa. As mentioned above, suchmeandering of data traffic adds latency to the packet data. Furthermore,transmission errors are also more prone to occur.

In the embodiment described below, a different approach is adopted. Thedata paths for the bearer traffic are chosen to be substantiallydifferent from the session initiation signaling paths.

With reference to FIG. 2, to begin with, suppose the MN 60 roams awayfrom the HN 54 toward the FN 56. Upon reaching the territory of the FN56, the MN 60 receives an advertisement message from the FN 56. From themessage, the MN MN 60 derives the address of the FA 66. Thereafter, theMN 60 reports back to the HN 54 by registering the address of the FA 66with the HA 62. The registered address is called the FA CoA which isstored in the routing table of the HA 62 in the HN 54.

Again, suppose the user of the MN 60 wants to have a video conferencingsession with the user of the CN 90 in the RN 58.

First, the MN obtains a CCoA from the FN 56. Using the HoA originallyassigned by the HA 62 in the HN 54, the MN 60 registers the CCoA withthe HA 62 in the HN 54. The MN 60 also registers with the S-CSCF 72 inthe HN 54 using the HoA for the access of the SIP (Session InitiationProtocol) network in the HN 54.

The MN 60 then sends a SIP INVITE message to the P-CSCF 70 in the HN 54.It should be noted that in actual operation, as with all other datatraffic, the SIP INVITE message first goes through the PDSN 68 and theHA 62 before routing to the P-CSCF 70. Furthermore, as well known in theart, the data traffic is in the form of electrical signals via a carrierwave traveling through the system 50. For the sake of clarity in amanner similarly described above, the data traffic is illustrated aslogical paths. That is, in the following description, unlessspecifically highlighted, only the logical paths of the data traffic aredepicted.

It further should be noted that the MN 60 can send the SIP INVITEmessage to the P-CSCF 71 in the FN 56 to initiate the conferencingsession as an alternative. For conciseness in explanation, in thefollowing description, the P-CSCF 70 in the HN 54 is used for theconference session initiation.

Returning to FIG. 2, the SIP INVITE message includes a descriptionportion called the SDP (Session Description Protocol) which in essencedescribes the basic requirements for the proper execution of therequested video conferencing session. For instance, included in the SDPare the IP address and port numbers of the MN 60, and the codecspecification for the session. More importantly, in this embodiment, theSDP includes the CCoA of the MN 60 for the media flow, that is thebearer traffic.

The P-CSCF 70 in the HN 54 is a node assuming the duty of call sessionmanagement. Upon receipt of the SIP INVITE message, the P-CSCF 70generates a token unique to the requested session. The P-CSCF 70 thenforward the SIP INVITE message to the S-CSCF 72 in the HN 54. The C-CSCF72 in turn sends the SIP INVITE message to the RN 58 for request ofacceptance.

Upon approval of the session by the S-CSCF 72 and the acceptance of theconferencing session by the CN 90 in the RN 58, the P-CSCF 70 sends thetoken to the MN 60. With the token in hand, the MN 60 in turn sends thetoken along with the requested QoS (Quality of Service) to the PDSN 68in the FN 56 to set up the bearer traffic, that is, the media flow ofaudio and video signals of the conferencing session.

The PDSN 68 then requests the authorized QoS for the conferencingsession from the PDF 75, which then relays the request to the P-CSCF 70in the HN 54. Any parameters granted by the PDF 75 have to be inconformance with certain mandated polices. Such policies may includerules dictated under the IMS/MMD standards, specific agreements amongnetworks, such as agreements between the HN 54 and the FN 56 relating tothe handling of the bearer traffic, policies particular to a network,such as policies unique only to the FN 56.

The PDF 75 is installed for the decision of all the imposed polices. Inthe decision process, the PDF 75 is interposed between the P-CSCF 71 andthe PDSN 68 in the FN 56. Furthermore, there is a Go interface 92interposed between the PDSN 68 and the PDF 75. There is yet another Gqinterface 94 disposed between the PDF 75 and the P-CSCF 71. The Go andGq interfaces 92 and 94 are used for policy control between theconferencing session and the bearer traffic. Details of the Go and Gqinterfaces can be found in the documents, 3GPP TS 23.107 published by3GPP, and 3GPP2 X.P0013-012 published by 3GPP2.

Returning now to FIG. 2, the requested session parameters, ifauthorized, are passed to the PDSN 68 from the P-CSCF 70 and the PDF 75.

In this embodiment, the CN 90 is assumed to have a CCoA which isassigned by the RN 58. Thus, upon receipt of the SIP INVITE messages,the CN 90 responds back with a SIP 200 OK message. The SIP 200 OKmessage basically reaffirms the parameters of the original SIP INVITEmessage. The SIP 200 OK follows the same data path as the SIP INVITEmessage but in the reverse order.

The MN 60 then confirms the receipt of the SIP 200 OK message by sendingan acknowledge message (ACK) back along the same data path as theoriginal SIP INVITE MESSAGE.

Bearer traffic is thereafter established by the PDSN 68 in the FN 56 inaccordance with the authorized parameters as set forth in the SIP INVITEmessage. In FIG. 2, the bearer data paths are shown as the video path100 and the audio path 102 directly linking the nodes 60 and 90 viatheir respective CCoA addresses. The bearer traffic in the manner asdescribed can sometimes be labeled as establishing data traffic usingthe CCoA under the simple IP, as different from the data paths 42 and 44in which the data paths are said to be set up using the CCoA under theMIP, as shown and described in FIG. 1.

In this embodiment, in the SIP INVITE, to specify the proper trafficflow, both the MN 60 and the CN 90 use their corresponding CCoAs. TheCCoA of the CN 90 can be assigned by the PDSN 78 of the RN 58, forexample. The CCoA of the MN 60 is assigned by and via a request to thePDSN 68 in the FN 56, for instance. A CCoA acquired in the manner asaforementioned is very often referred to as the “simple IP address.”

The process as stated above is shown in the flowchart of FIG. 3.

When the MN 60 roams to yet another network away from the FN 56, forinstance, to the FA 57, the MN 60 obtains a new CCoA from the new FN 57.Thereafter, the MN 60 registers the new CCoA with the HA 62 in the HN54. Since the MN 60 has previously used the HoA to register with theS-CSCF 72, the MN need not perform another SIP registration. In thisembodiment, the MN 60 merely sends a SIP UPDATE message with the newCCoA to the CN 90 in a manner substantially similar to the sending ofthe SIP INVITE message as previously described. For the sake ofconciseness, the logical flow of the SIP UPDATE message is not furtherrepeated here, but is shown in the flowchart of FIG. 4.

Reference is now returned to FIG. 2. Once the bearer traffic identifiedby the data paths 100 and 102 is established, in accordance with the IMSstandards, the PDSN 68 enforces a set of policies called the SBBC(Service Based Bearer Control) under the directions of the PDF 75. Theenforcement of the SBBC is continuous until the session between the MN60 and the CN 90 is terminated.

The policies include in the SBBC can be, among other things,authorization of the requested QoS for the session, charging of theindividual bearer flows, and policing of bearer traffic. To meet thisend, the PDSN 68 monitors the media flow in the bearer paths 100 and102. The operational details of the SBBC can be found in the documententitled, “3GPP2MMD Service Based Bearer Control Document, Work inProgress,” 3GPP2 X.P0013-012. Descriptions of the SDP can be found inthe document, entitled “IP Multimedia Call Control Protocol Based on Sipand SDP), Stage 3: TIA-873-004; and RFC 2327.

Operating in the manner as described above, contents of the media flowcan be sent and received straightforwardly as identified by the bearertraffic paths 100 and 102 shown in FIG. 2. Unnecessary detours of thedata paths can be curtailed, resulting in faster and more accuratereal-time data access.

FIG. 5 schematically shows the part of the hardware implementation of amobile node apparatus signified by the reference numeral 120 inaccordance with the invention. The apparatus 120 can be built andincorporated in various devices, such as a laptop computer, a PDA(Personal Digital Assistant) or a cellular phone.

The apparatus 120 comprises a central data bus 122 linking severalcircuits together. The circuits include a CPU (Central Processing Unit)or a controller 124, a receive circuit 126, a transmit circuit 128, anda memory circuit 130.

The receive and transmit circuits 126 and 128 can be connected to a RF(Radio Frequency) circuit but is not shown in the drawing. The receivecircuit 126 processes and buffers received signals before sending out tothe data bus 122. On the other hand, the transmit circuit 128 processesand buffers the data from the date bus 122 before sending out of thedevice 120. The CPU/controller 124 performs the function of datamanagement of the data bus 122 and further the function of general dataprocessing, including executing the instructional contents of the memorycircuit 130.

The memory circuit 130 includes a set of instructions generallysignified by the reference numeral 131. In this embodiment, theinstructions include, among other things, portions such as the MIPclient 132 and the SIP client 134. The SIP client 134 includes theinstructional sets in accordance with the invention as describedpreviously. The MIP client 132 includes the instructional sets forallowing the apparatus 120 to operate under the IP and the MIP, such asacquiring various types of addresses for various uses, also as describedabove.

In this embodiment, the memory circuit 130 is a RAM (Random AccessMemory) circuit. The exemplary instruction portions 132 and 134 aresoftware modules. The memory circuit 130 can be tied to another memorycircuit (not shown) which can either be of the volatile or nonvolatiletype. As an alternative, the memory circuit 130 can be made of othercircuit types, such as an EEPROM (Electrically Erasable ProgrammableRead Only Memory), an EPROM (Electrical Programmable Read Only Memory),a ROM (Read Only Memory), a magnetic disk, an optical disk, and otherswell known in the art.

Finally, described in the embodiments are only few networks tied to abackbone network. It should be apparent that a multiplicity of networkscan be involved. Furthermore, described in the embodiment, the node 60is depicted as a mobile device roaming through different foreignnetworks. It should be understand that the corresponding network node 90can be stationary. The node 90 can also be mobile, and when reachinganother foreign network, performs procedures and status update in amanner similar to that required of the node 60. Moreover, the process ofsignaling for initiation of the communication session need not beconfined to the use of the HoA as described in the embodiment. A CCoAcan be used instead of the HoA in the signaling process. In addition,any logical blocks, circuits, and algorithm steps described inconnection with the embodiments can be implemented in hardware,software, firmware, or combinations thereof. It will be understood bythose skilled in the art that theses and other changes in form anddetail may be made therein without departing from the scope and spiritof the invention.

1. A method in a wireless communication system, comprising: acquiring a first source address and a second source address of a mobile node located in a foreign network, wherein the first source address is a home address of the mobile node in a home network and the second source address is a co-located care-of address of the mobile node in the foreign network; signaling, using said first source address, a request to the home network to initialize a communication session between the mobile node in the foreign network and a correspondent node located in a remote network; and transmitting, from the foreign network to the remote network, contents of said communication session to the correspondent node using said second source address.
 2. The method of claim 1 further including signaling for initialization of said communication session via a first communication path, and transmitting said contents of said communication session via a second communication path.
 3. The method of claim 2 wherein said transmitting said contents includes transmitting said contents in a first foreign network, said method further including updating said co-located care of address during said transmitting said contents in a second foreign network.
 4. The method of claim 2, wherein the first communication path includes a session initiation signaling path and the second communication path includes a data traffic bearing path.
 5. The method of claim 1, wherein the signaling further comprises: transmitting, to the home network, a request to initiation the communication session; receiving, from the home network, a token confirming the correspondent node accepted an invitation sent from the home network to join the communication session; transmitting the token to the foreign network; and receiving, from the foreign network, confirmation that the communication session is established.
 6. An apparatus in a wireless communication system, comprising: means for acquiring first source address and second source address of a mobile node located in a foreign network, wherein the first source address is a home address of the mobile node in a home network and the second source address is a co-located care-of address of the mobile node in the foreign network; means for signaling, using said first source address, a request to the home network to initialize a communication session between the mobile node in the foreign network and a correspondent node located in a remote network; and means for transmitting, from the foreign network to the remote network, contents of said communication session to the correspondent node using said second source address.
 7. The apparatus of claim 6 further including means for signaling for initialization of said communication session via a first communication path, and means for transmitting said contents of said communication session via a second communication path.
 8. The apparatus of claim 7 further including means for updating said co-located care of address when said apparatus moves from one foreign network to another foreign network in said wireless communication system.
 9. The apparatus of claim 7, wherein the first communication path includes a session initiation signaling path and the second communication path includes a data traffic bearing path.
 10. The apparatus of claim 6, wherein the means for signaling further comprises: means for transmitting, to the home network, a request to initiation the communication session; means for receiving, from the home network, a token confirming the correspondent node accepted an invitation sent from the home network to join the communication session; means for transmitting the token to the foreign network; and means for receiving, from the foreign network, confirmation that the communication session is established.
 11. An apparatus in a communication system, comprising: a memory circuit having computer-readable instructions for acquiring first source address and second source address of a mobile node located in a foreign network, wherein the first source address is a home address of the mobile node in a home network and the second source address is a co-located care-of address of the mobile node in the foreign network, signaling, using said first source address, a request to the home network to initialize a communication session between the mobile node in the foreign network and a correspondent node located in a remote network, and transmitting, from the foreign network to the remote network, contents of said communication session to the correspondent node using said second source address; and a processor circuit coupled to said memory circuit for processing said computer-readable instructions.
 12. The apparatus of claim 11 wherein said memory circuit further including computer-readable instructions for signaling for initialization of said communication session via a first communication path, and transmitting said contents of said communication session via a second communication path.
 13. The apparatus of claim 12 wherein said memory circuit further including computer-readable instructions for updating said co-located care of address when said apparatus moves from a first foreign network to a second foreign network in said communication system.
 14. The apparatus of claim 11, wherein said memory circuit further including computer-readable instructions for: transmitting, to the home network, a request to initiation the communication session; receiving, from the home network, a token confirming the correspondent node accepted an invitation sent from the home network to join the communication session; transmitting the token to the foreign network; and receiving, from the foreign network, confirmation that the communication session is established.
 15. The apparatus of claim 11, wherein the first communication path includes a session initiation signaling path and the second communication path includes a data traffic bearing path.
 16. A Non-transitory computer-readable medium comprising computer-executable instructions for: acquiring first source address and second source address of a mobile node located in a foreign network, wherein the first source address is a home address of the mobile node in a home network and the second source address is a co-located care-of address of the mobile node in the foreign network; signaling, through a first communication path using said first source address, a request to the home network to initialize a communication session between the mobile node in the foreign network and a correspondent node located in a remote network; and transmitting contents of said communication session through a second communication path to the correspondent node using said second source address, wherein the second communication path runs between the foreign network to the remote network.
 17. The computer-readable medium of claim 16 further comprising computer-readable instructions for updating said second address when one of said first and second nodes moves from one network to another network in said wireless communication system.
 18. The computer-readable medium of claim 16 further comprising computer-readable instructions for transmitting, to the home network, a request to initiation the communication session; receiving, from the home network, a token confirming the correspondent node accepted an invitation sent from the home network to join the communication session; transmitting the token to the foreign network; and receiving, from the foreign network, confirmation that the communication session is established.
 19. The computer-readable medium of claim 16, wherein the first communication path includes a session initiation signaling path and the second communication path includes a data traffic bearing path. 